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Tesi sul tema "Stereochemistry"

Autore: Grafiati

Pubblicato: 4 giugno 2021

Ultima modifica: 30 luglio 2024

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1

Barr, Stephen Alexander. "Quinoline alkaloids : synthesis and stereochemistry". Thesis, Queen's University Belfast, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.333796.

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2

Kreisberg, Jennifer Diane. "Studies directed towards the total synthesis of the natural product diazonamide A". Access restricted to users with UT Austin EID Full text (PDF) from UMI/Dissertation Abstracts International, 2001. http://wwwlib.umi.com/cr/utexas/fullcit?p3037513.

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3

Holzbaur, Ines Elizabeth. "Control of stereochemistry in erythromycin biosynthesis". Thesis, University of Cambridge, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.624787.

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4

Silvary, Sunil Raj. "StereoElectronic Controls in the Preparation of 1-Benzyl-l, 2, 4, 5-Tetrahydro-(3H)-2-Benzazepin-3-ones Via Beckmann Rearrangement". Fogler Library, University of Maine, 2007. http://www.library.umaine.edu/theses/pdf/SilvarySR2007.pdf.

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5

Bates, Tim Frank. "The Stereochemistry of Silenes and Alpha-Lithio Silanes". Thesis, North Texas State University, 1987. https://digital.library.unt.edu/ark:/67531/metadc332323/.

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When E- or Z-l-methyl-l-phenyl-2-neopentylsilene was generated by the retro-Diels-Alder vacuum-sealed tube thermolysis of its corresponding anthracene adduct, in the presence of various alkoxysilanes, only one diastereomeric adduct was formed in each case, showing that the reactions are stereospecific. An x-ray crystal structure of the methoxytriphenylsilane adduct of the E-silene confirmed its relative configuration as (R,S) or (S,R). This demonstrated that the addition of alkoxysilanes to silenes is stereospecific and syn. The relative configurations of similar alkoxysilane and alkoxystannane adducts to E- and Z-l-methyl-l-phenyl-2-neopentylsilene were assigned based on a combination of xray structures and *3C NMR data. A strong, nonbonded oxygen-metal interaction is apparent in all of those compounds studied. Treatment of the alkoxystannane adducts with alkyl lithium reagents results in tin-lithium exchange in some cases. The results indicate that the resulting

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6

Pitt, A. R. "Stereochemistry and mechanism of isopenicillin N synthase". Thesis, University of Oxford, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.235052.

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7

Kennedy, D. A. "Crystallographic studies of relative and absolute stereochemistry". Thesis, Queen's University Belfast, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.373533.

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8

Okunishi, Tomoya. "Stereochemistry of Lignan Biosynthesis in Thymelaeaceae Plants". Kyoto University, 2003. http://hdl.handle.net/2433/149001.

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Kyoto University (京都大学)
0048
新制・課程博士
博士(農学)
甲第10276号
農博第1348号
新制||農||869(附属図書館)
学位論文||H15||N3797(農学部図書室)
UT51-2003-H697
京都大学大学院農学研究科応用生命科学専攻
(主査)教授島田幹夫, 教授桑原保正, 教授坂田完三
学位規則第4条第1項該当

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9

Alexander, Andrew James. "The dynamical stereochemistry of photon-initiated bimolecular reactions". Thesis, University of Oxford, 1997. http://ora.ox.ac.uk/objects/uuid:b50aaa50-5605-42e3-aa2a-4f4686df942f.

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The product state specific stereodynamics of the photon–initiated reaction of O(¹D₂) with H₂ has been investigated by polarised Doppler–resolved laser induced fluorescence, under room temperature bulb conditions. Product state resolved differential cross sections, excitation functions and rotational angular momentum alignments are reported for the following product channels, O(¹D₂) + H₂(¹Σ⁺_g ; v = 0) -> OH(X²Pi; v' = 0;N' = 14; f) + H(²S). at a mean collision energy of 12 kJ mol^-1. The data are compared with extensive state resolved quasi–classical trajectory (QCT) calculations of the linear and angular momentum distributions and excitation functions conducted on the Schinke–Lester (SL1) and K ab initio ground state (1¹A') potential energy surfaces. Overall, good agreement is obtained between the QCT calculated and experimentally determined stereodynamical features. The results are discussed in light of other recent work on this prototypical insertion reaction, and on the related systems of O(¹D₂) + HD and CH₄.

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10

Carroll, Jonathan G. "Structure, stereochemistry and reactions of aza-polycyclic metabolites". Thesis, Queen's University Belfast, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.322770.

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11

Dunlop, Robert. "Synthesis, stereochemistry and metabolism of small ring heterocycles". Thesis, Queen's University Belfast, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.317057.

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12

Fallah, Asadollah. "Stereochemistry and reactivity of some 1,3-heterocyclic compounds". Thesis, University of Portsmouth, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.328185.

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13

Turner, Helen Louise. "Absolute stereochemistry : the merits of VCD and XRD". Thesis, University of Southampton, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.430715.

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14

Adam, Michael Alexander. "Stereochemistry of crotylboronate additions to α, β-dialkoxyaldehydes". Thesis, Massachusetts Institute of Technology, 1985. http://hdl.handle.net/1721.1/15125.

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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Chemistry, 1985.
MICROFICHE COPY AVAILABLE IN ARCHIVES AND SCIENCE
Includes bibliographies.
by Michael Alexander Adam.
Ph.D.

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15

Pang, Kah Ling Christine. "The stereochemistry of the SE2' reactions of propargylsilanes". Thesis, University of Cambridge, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.620320.

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16

Kwan, David Howe. "The stereochemistry of reduction in modular polyketide synthases". Thesis, University of Cambridge, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.611514.

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17

Morgan, Ian Trevor. "The stereochemistry of some E' and S_E2' reactions". Thesis, University of Cambridge, 1991. https://www.repository.cam.ac.uk/handle/1810/271907.

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18

Jones, Graeme Robert. "The stereochemistry of electrophilic attack on chiral dienylmethylsilanes". Thesis, University of Cambridge, 1992. https://www.repository.cam.ac.uk/handle/1810/272534.

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19

Zhang, Yiqun. "Stereochemistry of small molecules: Configurational and conformational control". Diss., Virginia Tech, 2007. http://hdl.handle.net/10919/26535.

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Abstract (sommario):

Stereochemistry is important aspect of chemistry that customarily includes the study of the relative spatial arrangement of atoms within molecules (static stereochemistry), and the study of the stereochemical requirements and outcomes of chemical reactions (dynamic stereochemistry). These two branches complement each other in modern stereochemistry. Chiral organometallics feature prominently in organic synthesis as reactive intermediates. The possibility of exploring their stereochemistry in synthesis is associated with the configurational stability of the metal-bearing stereogenic center. We were interested in the configurational stability of lithiated and magnesiated nitriles. We developed a new series of lithio-cyclopropylnitriles bearing chelating groups for intramolecular coordination, as a possible strategy to impart configurational stability. Although this strategy has not yet been successful, using density functional theory (DFT) method, we addressed the effect of chelating groups on racemization via the â conducted tourâ mechanism. We then explored metal-bromine exchange on enantiopure bromonitrile as alternative route to metalated nitriles. In this way, we demonstrated that magnesiated 2,2-diphenyl cyclopropylnitrile is configurationally stable on the macroscopic timescale. No other metallated nitrile has ever demonstrated configurational stability on this timescale. In contrast, bromine-lithium exchange of 1-bromo-2,2-diphenyl-cyclopropylnitrile demonstrated fast racemization under the same conditions. Another major project focused on conformational control of acyclic molecules. Using X-ray crystallography and NMR spectroscopy, we found that the 2,6-disubstituted aryl group eclipses its geminal hydrogen, and induces an antiperiplanar relationship of the geminal and vicinal hydrogens. Interestingly, anti-nitrile aldols or syn-ketone aldols bearing 2,6-disubstituted aryl groups demonstrate unanticipated remote effects on acyclic conformation: the 2,6-disubstituted aryl group prefers to be in a gauche position to the largest vicinal group. The minimization of allylic 1,3-strain and syn-pentane-like interaction works together in establishing this conformational preference.
Ph. D.

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20

Truneh, A. "The stereochemistry of some rearrangement reactions of steroids". Thesis, University of Sussex, 1987. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.382483.

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21

Bower, Justin F. "Stereocontrol with 2-oxazolines". Thesis, Loughborough University, 1996. https://dspace.lboro.ac.uk/2134/10427.

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22

Tidswell, Edward C. "Anaerobic cometabolism : chiral bioreductions". Thesis, Aberystwyth University, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.342880.

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23

Emery, Vincent Clive. "Mechanistic aspects of bacteriochlorophyll A biosynthesis in Rhodopseudomonas sphaeroides". Thesis, University of Southampton, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.259664.

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24

Manickavasagar, Revathy. "The chemistry of B-norsteroids". Thesis, University of Sussex, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.357615.

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25

Leslie, Colin Philip. "Stereochemistry of the S[E]2 reaction of pentadienylsilanes". Thesis, University of Cambridge, 1995. https://www.repository.cam.ac.uk/handle/1810/251946.

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26

Roberts, Ieuan Owain. "The absolute stereochemistry of various naturally occurring fatty acids". Thesis, Bangor University, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.429867.

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27

London, Laurisa A. "The effect of stereochemistry and conformation on nanocomposites formation". DigitalCommons@Robert W. Woodruff Library, Atlanta University Center, 2013. http://digitalcommons.auctr.edu/dissertations/1590.

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28

Tahanpesar, Elham. "Studies of the synthesis of cyclodextrins with novel stereochemistry". Thesis, Cardiff University, 2007. http://orca.cf.ac.uk/54588/.

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Proton-deuterium exchange of the carbinol hydrogens of gluco-, manno- and galacto-methyl- ot-D-pyranosides with deuterium oxide catalysed by ultrasonicated Raney nickel had low regioselectivity. 4,6-0-Benzylidene-methyl-cc-D-glucopyranoside underwent deuteration at C- 2 and C-3 and cleavage of the benzylidene group, whereas 4,6-O-isopropylidene-methyl-a-D- glucopyranoside was deuterated exclusively at C-2 (2H-NMR), which provides a rapid and economical route to 2- 2Hi -methyl-a-D-glucopyranoside. The diol moiety of 4,6-0-benzylidene-methyl-a-D-glucopyranoside was cleaved under aqueous (sodium periodate), and non-aqueous (periodic acid) conditions to give a D-erythritol in high yield (80%, 90%). Application of similar conditions to heptakis{6-0-tert- butyldimethylsilyl)-p-cyclodextrin failed to give an isolable product. The epoxides methyl 2,3-anhydro-4,6-(9-benzylidene-methyl-a-D-mannopyranoside and /z67ta£w(2,3-anhydro)-f3-cyclomannin were prepared via the C2-tosylates. Both reacted with 4-ter/-butylbenzylthiol at the 3-position. The cyclomannin gave an adduct with xQ&,-altro stereochemistry as determined by NMR and the homogeneity was established by MALDI-MS (M+K+, m/z 3109.5, Ci6iH26602sS7Si7K). The mannopyranoside similarly reacted with L- cysteine to give a 4Ci-a//ro-amino acid sugar adduct, but the cyclomannin failed to react. The benzylidene-, isopropylidene- glucopyranosides and the silylated cyclodextrin mentioned above underwent allylation with allyl bromide, to give 2,3-di-O-allyl-glucopyranosides and heptakis(2,3-di-0-allyl)-p-CD respectively. Ring closing metathesis (RCM) with Grubb's 2nd generation catalyst of the allylated cyclodextrin yielded a complex mixture, but the allylated glucopyranosides yielded the cyclo-octenes, which were hydrogenated. Unexpectedly, the benzylidene protecting group was partially cleaved during RCM. All NMR spectra were assigned by correlation methods.

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29

Cook, Anthony Peter Fendick. "A treatment of stereochemistry in computer aided organic synthesis". Thesis, University of Leeds, 2015. http://etheses.whiterose.ac.uk/9147/.

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This thesis describes the author’s contributions to a new stereochemical processing module constructed for the ARChem retrosynthesis program. The purpose of the module is to add the ability to perform enantioselective and diastereoselective retrosynthetic disconnections and generate appropriate precursor molecules. The module uses evidence based rules generated from a large database of literature reactions. Chapter 1 provides an introduction and critical review of the published body of work for computer aided synthesis design. The role of computer perception of key structural features (rings, functions groups etc.) and the construction and use of reaction transforms for generating precursors is discussed. Emphasis is also given to the application of strategies in retrosynthetic analysis. The availability of large reaction databases has enabled a new generation of retrosynthesis design programs to be developed that use automatically generated transforms assembled from published reactions. A brief description of the transform generation method employed by ARChem is given. Chapter 2 describes the algorithms devised by the author for handling the computer recognition and representation of the stereochemical features found in molecule and reaction scheme diagrams. The approach is generalised and uses flexible recognition patterns to transform information found in chemical diagrams into concise stereo descriptors for computer processing. An algorithm for efficiently comparing and classifying pairs of stereo descriptors is described. This algorithm is central for solving the stereochemical constraints in a variety of substructure matching problems addressed in chapter 3. The concise representation of reactions and transform rules as hyperstructure graphs is described. Chapter 3 is concerned with the efficient and reliable detection of stereochemical symmetry in both molecules, reactions and rules. A novel symmetry perception algorithm, based on a constraints satisfaction problem (CSP) solver, is described. The use of a CSP solver to implement an isomorph‐free matching algorithm for stereochemical substructure matching is detailed. The prime function of this algorithm is to seek out unique retron locations in target molecules and then to generate precursor molecules without duplications due to symmetry. Novel algorithms for classifying asymmetric, pseudo‐asymmetric and symmetric stereocentres; meso, centro, and C2 symmetric molecules; and the stereotopicity of trigonal (sp2) centres are described. Chapter 4 introduces and formalises the annotated structural language used to create both retrosynthetic rules and the patterns used for functional group recognition. A novel functional group recognition package is described along with its use to detect important electronic features such as electron‐withdrawing or donating groups and leaving groups. The functional groups and electronic features are used as constraints in retron rules to improve transform relevance. Chapter 5 details the approach taken to design detailed stereoselective and substrate controlled transforms from organised hierarchies of rules. The rules employ a rich set of constraints annotations that concisely describe the keying retrons. The application of the transforms for collating evidence based scoring parameters from published reaction examples is described. A survey of available reaction databases and the techniques for mining stereoselective reactions is demonstrated. A data mining tool was developed for finding the best reputable stereoselective reaction types for coding as transforms. For various reasons it was not possible during the research period to fully integrate this work with the ARChem program. Instead, Chapter 6 introduces a novel one‐step retrosynthesis module to test the developed transforms. The retrosynthesis algorithms use the organisation of the transform rule hierarchy to efficiently locate the best retron matches using all applicable stereoselective transforms. This module was tested using a small set of selected target molecules and the generated routes were ranked using a series of measured parameters including: stereocentre clearance and bond cleavage; example reputation; estimated stereoselectivity with reliability; and evidence of tolerated functional groups. In addition a method for detecting regioselectivity issues is presented. This work presents a number of algorithms using common set and graph theory operations and notations. Appendix A lists the set theory symbols and meanings. Appendix B summarises and defines the common graph theory terminology used throughout this thesis.

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30

Riley, Andrew M. "Inositol phosphates and analogues : synthesis, stereochemistry and molecular recognition". Thesis, University of Bath, 1996. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.484225.

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31

McLamore, Dolores Sherita. "Determination of the relative stereochemistry of adducts resulting from the addition lithium dienolates to Michael acceptors". Thesis, Virginia Tech, 1994. http://hdl.handle.net/10919/43137.

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The addition of the lithium dienolate of ethyl crotonate to 2-cyclopentenone was studied to determine the stereochemical outcome of this Michael addition. Proof of the stereochemistry was provided via the unambiguous synthesis and comparison of ketone 73 from norcamphor 85.
Master of Science

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32

Schuff, Brandon Patrick. "Palladium (II)-catalyzed stereoselective formation of [alpha]-O-glycosides". Thesis, Montana State University, 2007. http://etd.lib.montana.edu/etd/2007/schuff/SchuffB0507.pdf.

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33

Tang, Yongping. "Investigation of the stereochemistry of macrocyclic ligand complexes: [Ni(tetramethylcyclam)][superscript]2+ and [brace]Co(Me[subscript]6[14]dieneN[subscript]4)CI[subscript]2+[brace]". Thesis, Georgia Institute of Technology, 1990. http://hdl.handle.net/1853/26951.

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34

Laffosse, Miguel Diaz. "Stereoselective carbon-carbon bond formation via sulfur stabilized carbanions". Thesis, Georgia Institute of Technology, 1985. http://hdl.handle.net/1853/27171.

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35

Corry, Denis Albert Kenneth. "Mechanistic and microstructural analysis of ring-opening metathesis polymerisation". Thesis, Queen's University Belfast, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.266699.

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36

Russel, A. T. "Stereocontrol in organic chemistry : Some new approaches". Thesis, University of Salford, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.381701.

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37

Uppal, Sukhjinder Singh. "Preparation of η³-allylmolybdenum complexes using cis-Mo(CO)₄(THF)₂ : application to the synthesis of methyl pseudomonate C". Thesis, University of Leeds, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.275796.

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38

Boote, Craig. "Structural studies of deoxyribonucleic acids using diffraction and spectroscopic methods". Thesis, Keele University, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.287969.

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39

Collett, Lynne Alison. "Structural and stereochemical investigations of terrestrial and marine pyrone metabolites". Thesis, Rhodes University, 1997. http://hdl.handle.net/10962/d1005013.

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This thesis presents an investigation into the chemistry of 6 substituted 5, 6-dihydro-a-pyrone compounds. A comprehensive review of these compounds was published in 1989 and the subsequent literature is covered in an updated review presented below. Eight 6-substituted 5,6-dihydro-a-pyrone metabolites from three different South African plant species Cryptocarya latijolia, Syncolostemon densiflorus, and Syncolostemon argenteus have been the subject of structural and stereochemical investigations. The absolute stereochemistry of the known compound "triacetate" from C. latijolia has been established as 6R-[2R,4S,6S-(triacetyloxy)heptylJ-5,6-dihydro-2H-pyran-2-one (74) using CD and acetonide formation with subsequent application of the modified Moshers method. The absolute stereochemistry of the related metabolite "diacetate", also from C. latijolia, has been assigned as 6R-[2S,4S-diacetyloxypentylJ-5,6-dihydro-2H-pyran-2-one (76). In addition, the outstanding stereochemistry at C-5' in syndenolide, from S. densiflorus, followed from conversion to its diacetonide and subsequent NMR analysis. Syndenolide is therefore 6R-[5S-(acetoxy)-IR,2R,3S-(trihydroxy)-heptylJ-5,6- dihydro-2H -pyran-2-one. The genus Syncolostemon has proved to be a rich source of a-pyrone compounds and the chemistry of S. argenteus, not investigated previously, was examined as part of an ongoing search for new 5,6-dihydro-a-pyrones. The study yielded five new a-pyrone natural products, synargentolide A-E. The structure of synargentolide A (82) has been assigned as 6R[4R,5R,6S-triacetyloxy-lE-heptenylJ-5,6-dihydro-2H-pyran-2-one using CD and NMR techniques. The structures of synargentolide B (87), C (92) and E (94) also followed from a detailed NMR analysis and the stereochemistry tentatively assigned based on CD and NMR data. Synargentolide D (93) was thermally unstable, and a paucity of material prevented stereochemical investigations, however the structure was determined from initial NMR analysis. The marine molluscs of the genus Siphonaria have only become the subject of chemical studies in the last fifteen years. These molluscs characteristically produce polypropionate type natural products. A review of Siphonarian polypropionate metabolites containing a pyrone functionality is presented. Examination of an endemic South African species Siphonaria serrata yielded one novel polypropionate metabolite containing a ),-pyrone functionality, siserrone A (131). The structure of this compound was unambiguously established using standard NMR experiments. The relative stereochemisty of the hemi-ketal moiety was assigned from a careful analysis of the ROESY NMR spectrum and the stereochemisty of the acyclic portion determined from a comparison of the 13C and 'H NMR data of a degradation product with the corresponding data of a synthetic compound. It was also established that the modified Moshers method could not be used to determine the absolute stereochemistry of the secondary hydroxy I substituent at C-11. The absolute stereochemistry of 131 was thus assigned in accordance with the proven stereochemistry of Siphonarian metabolites.

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40

Beck, Daniel Antony Speedie. "Stereoselective intramolecular Michael addition reactions of pyrrole and their application to natural product syntheses /". View thesis entry in Australian Digital Theses Program, 2006. http://thesis.anu.edu.au/public/adt-ANU20070130.130009/index.html.

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41

Shen, Lan. "Studies directed toward the syntheses of cyathins and diazonamides /". Digital version accessible at:, 1999. http://wwwlib.umi.com/cr/utexas/main.

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42

Hemperly, Susan Barbara. "Mechanistic studies of diastereoselective cyclopropanations of homochiral ene-ketals and synthesis and resolution of diastereomeric alpha-hydroxycycloalkanone ketals". Diss., The University of Arizona, 1989. http://hdl.handle.net/10150/184886.

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Abstract (sommario):

A series of homochiral ene ketals were prepared and subjected to the Simmons-Smith cyclopropanation. A mechanistic model was formulated to explain the observed diastereoselectivity seen for the common ring systems. Diastereoselectivity is thought to result from preferential chelation of the Simmons-Smith reagent at the least sterically hindered lone pair of electrons on the dioxolane oxygen proximal to the alkene. The role of dioxolane oxygen was inferred from studies with a hydrocarbon model system. The effect of cyclohexene ring conformation on the diastereoselectivity was examined for conformationally restricted ene ketal systems. Reagent chelation by the pseudoequatorial dioxolane oxygen atom was shown to be favored. This preference can either antagonize or reinforce diastereoselectivity due to steric hindrance of the dioxolane oxygen atoms from dissymmetric placement of the appendages on the dioxolane ring. A general method for the chromatographic resolution of diastereomeric α-hydroxycycloalkanone ketals derived from 1,4-di-O-benzyl-L-threitol is reported. Separability is thought to result from differences in intramolecular hydrogen bonding for the two diastereomeric forms.

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43

Cooper, Andrew Donovan. "Resolution of enantiomers using cyclodextrins in NMR and HPLC". Thesis, University of Bath, 1991. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.292808.

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44

Li, Manqing. "The stereochemistry of substituent effects in alpha-sulfonyl carbanion formation". Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2000. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape3/PQDD_0018/NQ58146.pdf.

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45

Sun, Han. "Stereochemistry of Challenging Natural Products Studied by NMR-based Methods". Doctoral thesis, Niedersächsische Staats- und Universitätsbibliothek Göttingen, 2012. http://hdl.handle.net/11858/00-1735-0000-000D-FD1A-F.

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46

Hamilton, Lynne. "Synthesis, stereochemistry and reactions of quinoline, isoquinoline and acridine metabolites". Thesis, Queen's University Belfast, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.334710.

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47

O'Loughlin, Julian Matthew Adrian. "Control of absolute stereochemistry in the aza-(2,3)-Wittig rearrangement". Thesis, University of Nottingham, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.415867.

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48

Vergnolle, Olivia. "The stereochemistry of dehydration in the Borrelidin modular polyketide synthase". Thesis, University of Cambridge, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.611827.

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49

Geesi, Mohammed. "A synthetic approach to determine the stereochemistry of diepomuricanin A". Thesis, University of Southampton, 2014. https://eprints.soton.ac.uk/369347/.

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Abstract (sommario):

The total synthesis of bis-epoxide acetogenin, diepomuricanin, has been investigated in order to determine the absolute stereochemistry within the bis-epoxide region. Two approaches (linear and tethered-metathesis) were attempted. In the linear approach, two routes were investigated. In the first one an intermediate aldehyde 248 was created in six steps in order to investigate the asymmetric α-oxidation and diastereoselective additions of organometallic reagents. Model studies using octanal met with moderate success, and highlighted the sensitivity of the α-oxidation products. The instability of the α-oxidation products prevented a proper study of the additions of Grignard and organozinc reagents. In a second route, hydrolytic kinetic resolution of terminal epoxides was investigated in order to obtain optically enriched 1,2-diols suitable for elaboration to diepomuricanins. A revised, convergent approach to diepomuricanin A stereoisomers was developed based on a silicon-tethered metathesis of allylic alcohol fragments. Sharpless asymmetric kinetic resolution (SAKR) of allylic alcohols (±)-305 and (±)-306 was the key step towards the left hand fragments (19S,20S)-302, and (19R,20R)-302, and the right hand fragments (15S,16S)-303, and (15R,16R)-303. Combining them together via a tethered alkene metathesis, led to the key siloxytriene 308. An investigation of the Alder-ene reactions of right hand fragment (15S,16S)-303 display the low selectivity of the less hindered and more electron-rich C27-C28 doble bond. Therefore, the route was modified to proceed by new right hand fragment epoxyalcohols (15S,16S)-354, and (15R,16R)-354, which allowed formation of butenolide 363 towards the synthesis of the diepomuricanin A stereoisomer (anti-5d).

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50

Buckle, Michael James Christopher. "The stereochemistry of some SE2' reactions of allylsilanes and allenylsilanes". Thesis, University of Cambridge, 1993. https://www.repository.cam.ac.uk/handle/1810/272372.

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